NEW YORK — Some fans of Jessica Chastain and Dan Stevens may find their casting in the new Broadway revival of The Heiress a bit confounding.

Chastain, 35, the ravishing redhead who won an Oscar nomination for The Help, plays Catherine Sloper, a shy plain Jane who stands to inherit a fortune from her emotionally distant father. Stevens, a 30-year-old Brit best known on this side of the Atlantic as dreamboat/mensch Matthew Crawley on TV's Downton Abbey, turns up as Morris Townsend, a wily suitor whose sudden interest in Catherine rouses both her hopes and her dad's suspicion.

For those unfamiliar with the play — based on the Henry James novel Washington Square, and adapted into a 1949 film — suffice it to say that neither Catherine's dreams nor Morris' are fulfilled. But chatting over coffee before a recent rehearsal, the actors discuss their characters without pity or scorn. In fact, both approached this Heiress, which opens Thursday at the Walter Kerr Theatre, intent on revealing its central couple to be more complex than appearances suggest.

For Chastain, that meant disproving Catherine's father's notion of her as a dull, dim-witted wallflower. "Someone may see her as not clever, but to me, it's more that she's always honest. And that openness and purity are beautiful."

That interpretation proved a perfect entry point for Stevens, who had never seen the play before but gleans that Morris "may traditionally be more villainous, more obviously after (Catherine)'s money early in the play. We talked about playing with people's preconceptions of him."

Preconceptions of the actor who plays such a good-hearted hunk on television were also a factor. "If people think, 'Oh, Matthew Crawley's playing Morris Townsend — he's a nice guy,' that's great," Stevens says mischievously. "We just asked, what if Morris is in love with both Catherine and her things? She has attractive qualities; it's not like she's this hideous creature who just crawled out from under a rock."

Certainly not in this production — though Chastain downplays her willowy beauty, both on stage and in conversation. "Last year I had so many movies come out, and in the one I got the Oscar (nod) for I played this sexpot and looked the best I'll ever look in my life. Before that, I never once heard that I was too pretty for a role. I'd hear the opposite, in fact."

Though Chastain and Stevens are making their Broadway debuts in Heiress, both got their start in theater; she last trod the boards in a controversial 2009 staging of Othello, directed by Peter Sellars and starring Philip Seymour Hoffman as Iago.

"That was tough," Chastain admits. "It was a nine-month commitment; we traveled around the world and it was a polarizing production. So I knew that when I came back on stage, it had to be the right experience."

So far, so good, says the actress, whose next movie, Kathryn Bigelow's Zero Dark Thirty, is due Dec. 19. She's already generating more Oscar buzz for her role as a CIA operative who picks up Osama bin Laden's trail. "I just saw the film the other day, and it's incredible," she says. "I'd always wanted to work with Kathryn. And this is just a great female role; it reminded me, when I read the script, of Jodie Foster's (character) in The Silence of the Lambs." (Bigelow's last film, The Hurt Locker, won the Oscar for best picture in 2010.)

Stevens appears next as a female vampire's boyfriend in Amy Heckerling's Vamps, out Friday, "a really cute, kooky film with Amy's inimitable stamp all over it." Of his future on Downton Abbey, he quips, "I have no idea what's going to happen — and if I did, I wouldn't tell anyone."

For now, both are enjoying their time on the boards. "We have a great team, which is important — because in a play, one bad apple can ruin a whole group's energy," she says. "Having to kiss someone I don't like for six months — can you imagine? Thank God Dan's lovely and wonderful."

Stevens blushes a bit, then recovers. "You want to do a movie together?"

Chastain beams. "Let's do it! Let's make The Heiress into a movie. You bring your wife and kids, and I'll bring my boyfriend. We'll make it a holiday."